System and method for measuring depth of instrumentation

ABSTRACT

Devices, systems, and methods for measuring the distance and/or depth to a target bone for surgery using a robotic surgical system. The surgical robot system may be configured to depict the distance from a guide tube of the robot to a target bone of a patient as a vector. The vector may represent a view of the guide tube when the guide tube&#39;s central axis is coincident with a line of intersection of two viewplanes of a 2D image of the target bone, for example, one viewplane being sagittal and one viewplane being axial.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 15/157,444 filed May 18, 2016, which is a continuation-in-partapplication of U.S. patent application Ser. No. 15/095,883 filed on Apr.11, 2016 (published as U.S. Patent Publication No. 2016/0220320 A1),which is a continuation-in-part application of U.S. patent applicationSer. No. 14/062,707 filed on Oct. 24, 2013 (published as U.S. PatentPublication No. 2014/0275955 A1), which is a continuation-in-partapplication of U.S. patent application Ser. No. 13/924,505 filed on Jun.21, 2013 (published as U.S. Patent Publication No. 2013/0345718 A1, withcorrected publication as U.S. Patent Publication No. 2016/0242849 A9),which is a nonprovisional patent application that claims priority toU.S. provisional patent application No. 61/662,702 filed on Jun. 21,2012, and claims priority to U.S. provisional patent application No.61/800,527 filed on Mar. 15, 2013, the entire contents of all of whichare incorporated herein by reference.

FIELD OF THE INVENTION

The present disclosure relates to position recognition systems, and inparticular, position recognition systems that allow measurement ofinstrumentation and tools in a patient using robot-assisted surgicaltechniques.

BACKGROUND OF THE INVENTION

Various medical procedures require the accurate localization of athree-dimensional position of a surgical instrument within the body inorder to effect optimized treatment. For example, some surgicalprocedures to fuse vertebrae require that a surgeon drill multiple holesinto the bone structure at specific locations. To achieve high levels ofmechanical integrity in the fusing system, and to balance the forcescreated in the bone structure, it is necessary that the holes aredrilled at the correct location. Vertebrae, like most bone structures,have complex shapes including non-planar curved surfaces making accurateand perpendicular drilling difficult. Conventionally, a surgeon manuallyholds and positions a drill guide tube by using a guidance system tooverlay the drill tube's position onto a three dimensional image of thebone structure. This manual process is both tedious and time consuming.The success of the surgery is largely dependent upon the dexterity ofthe surgeon who performs it.

When a surgeon performs minimally invasive surgery and prepares to placea screw into bone, it is often desirable to insert a dilator tube fromthe surface of the skin through muscle and connective tissue down to aposition where the distal end of the dilator tube is adjacent to bone.The dilator tube serves as a corridor through which drilling and othersurgical steps can occur. Currently, the most frequently used method forgauging whether the dilator is sufficiently far enough inserted is torecord x-ray images, which is effective but exposes the patient andsurgical staff to x-rays and can be time consuming. If image guidancewere to be used instead of x-rays, it would spare the patient and staffsome exposure to x-rays. However, a tracking array mounted on a dilatortube has the drawbacks that it is unwieldy and obtrusive to the surgeonin an area where a great deal of surgical activity is occurring.

Thus, there is a need to be able to measure the depth of surgicalinstrumentation in a manner that limits the exposure of the patient andmedical staff to unnecessary radiation from imaging systems withoutobstructing and impeding a medical staff's ability to perform thesurgical operation on the patient. The present disclosure overcomes thedisadvantages of current traditional surgical techniques androbot-assisted surgical techniques. For example, using known positionsof components of a robot surgical system allows a surgeon to position along shaft such as a dilator tube within a secondary tracked tube, suchas the robot's end effector guide tube or a free tracked external guidetube, to a depth such that the dilator tube contacts the target bonystructure. This positioning would allow tracking the dilator tubeindirectly without tracking the dilator itself and without the use ofx-ray images as it is further inserted into a patient.

SUMMARY OF THE INVENTION

To meet this and other needs, devices, systems, and methods fordetermining the distance or depth for a surgical instrument to contact atarget bone of a patient during robot assisted surgery is provided.

According to one exemplary embodiment, a surgical robot system may beconfigured to determine a distance for a surgical instrument to contacta target bone of a patient during a surgical operation. The system mayinclude a guide tube comprising a tracking marker and wherein the guidetube may be configured to receive the surgical instrument, a trackingsubsystem having a position sensor that recognizes the tracking markerin a navigational space, a platform interface module that may beconfigured to receive a signal from the tracking subsystem indicative ofa position of the guide tube based on the tracking marker, and acomputer subsystem, including a computer and a display, that may beconfigured to receive a first viewplane scan of the target bone and asecond viewplane scan of the target bone. The first viewplane and thesecond viewplane may form an intersection of views of the target bone.The computer subsystem may also be configured to receive the position ofthe guide tube from the platform interface module and may depict avector indicative of the distance to contact the target bone of thepatient, relative to a distal portion of the guide tube, on at least oneof the first viewplane scan and the second viewplane scan, and whereinthe vector may represent a central axis of the guide tube beingcoincident to the intersection.

According to another embodiment, a method for determining the distancefor a surgical instrument to contact a target bone of a patient during asurgical operating using a robotic surgical system may be provided. Themethod may include receiving, by a computer subsystem having a computerand a display, a first viewplane scan of the target bone and a secondviewplane scan of the target bone, wherein the first viewplane and thesecond viewplane form an intersection of views of the target bone in animage space. The method may also include receiving, by the computersubsystem, a position of a guide tube in navigational space, anddetermining, by the computer, a distance between a distal portion of theguide tube to the target bone of the patient, wherein the distance maybe determined such that a central axis of the guide tube is coincidentto the intersection. The method may also include depicting, via thedisplay, a vector indicative of the distance to contact the target boneof the patient on at least one of the first viewplane scan and thesecond viewplane scan.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and the following detailed description of certainembodiments thereof may be understood by reference to the followingfigures:

FIG. 1 is an overhead view of a potential arrangement for locations ofthe robotic system, patient, surgeon, and other medical personnel duringa surgical procedure;

FIG. 2 illustrates the robotic system including positioning of thesurgical robot and the camera relative to the patient according to oneembodiment;

FIG. 3 illustrates a surgical robotic system in accordance with anexemplary embodiment;

FIG. 4 illustrates a portion of a surgical robot in accordance with anexemplary embodiment;

FIG. 5 illustrates a block diagram of a surgical robot in accordancewith an exemplary embodiment;

FIG. 6 illustrates a surgical robot in accordance with an exemplaryembodiment;

FIGS. 7A-7C illustrate an end effector in accordance with an exemplaryembodiment;

FIG. 8 illustrates a surgical instrument and the end effector, beforeand after, inserting the surgical instrument into the guide tube of theend effector according to one embodiment;

FIGS. 9A-9C illustrate portions of an end effector and robot arm inaccordance with an exemplary embodiment;

FIG. 10 illustrates a dynamic reference array, an imaging array, andother components in accordance with an exemplary embodiment;

FIG. 11 illustrates a method of registration in accordance with anexemplary embodiment;

FIG. 12A-12B illustrate embodiments of imaging devices according toexemplary embodiments;

FIG. 13 illustrates an exemplary image of a viewplane x-ray withassociated depictions measuring depth to a target bone;

FIG. 14 illustrates an exemplary image of a viewplane of an x-ray withassociated depictions measuring depth to a target bone;

FIG. 15 illustrates an exemplary image of a viewplane of an x-ray withassociated depictions measuring depth to a target bone;

FIG. 16 illustrates an exemplary image of a viewplane of an x-ray withassociated depictions measuring depth to a target bone;

FIG. 17 illustrates an exemplary image of a viewplane of an x-ray withassociated depictions measuring depth to a target bone;

FIG. 18 illustrates an exemplary instrument with markings consistentwith the present disclosure;

FIG. 19 illustrates an exemplary instrument and guide tube consistentwith the present disclosure;

FIG. 20 illustrates an exemplary method consistent with the presentdisclosure.

DETAILED DESCRIPTION OF THE INVENTION

It is to be understood that the present disclosure is not limited in itsapplication to the details of construction and the arrangement ofcomponents set forth in the description herein or illustrated in thedrawings. The teachings of the present disclosure may be used andpracticed in other embodiments and practiced or carried out in variousways. Also, it is to be understood that the phraseology and terminologyused herein is for the purpose of description and should not be regardedas limiting. The use of “including,” “comprising,” or “having” andvariations thereof herein is meant to encompass the items listedthereafter and equivalents thereof as well as additional items. Unlessspecified or limited otherwise, the terms “mounted,” “connected,”“supported,” and “coupled” and variations thereof are used broadly andencompass both direct and indirect mountings, connections, supports, andcouplings. Further, “connected” and “coupled” are not restricted tophysical or mechanical connections or couplings.

The following discussion is presented to enable a person skilled in theart to make and use embodiments of the present disclosure. Variousmodifications to the illustrated embodiments will be readily apparent tothose skilled in the art, and the principles herein can be applied toother embodiments and applications without departing from embodiments ofthe present disclosure. Thus, the embodiments are not intended to belimited to embodiments shown, but are to be accorded the widest scopeconsistent with the principles and features disclosed herein. Thefollowing detailed description is to be read with reference to thefigures, in which like elements in different figures have like referencenumerals. The figures, which are not necessarily to scale, depictselected embodiments and are not intended to limit the scope of theembodiments. Skilled artisans will recognize the examples providedherein have many useful alternatives and fall within the scope of theembodiments.

Turning now to the drawing, FIGS. 1 and 2 illustrate a surgical robotsystem 100 in accordance with an exemplary embodiment. Surgical robotsystem 100 may include, for example, a surgical robot 102, one or morerobot arms 104, a base 106, a display 110, an end effector 112, forexample, including a guide tube 114, and one or more tracking markers118. The surgical robot system 100 may include a patient tracking device116 also including one or more tracking markers 118, which is adapted tobe secured directly to the patient 210 (e.g., to the bone of the patient210). The surgical robot system 100 may also utilize a camera 200, forexample, positioned on a camera stand 202. The camera stand 202 can haveany suitable configuration to move, orient, and support the camera 200in a desired position. The camera 200 may include any suitable camera orcameras, such as one or more infrared cameras (e.g., bifocal orstereophotogrammetric cameras), able to identify, for example, activeand passive tracking markers 118 in a given measurement volume viewablefrom the perspective of the camera 200. The camera 200 may scan thegiven measurement volume and detect the light that comes from themarkers 118 in order to identify and determine the position of themarkers 118 in three dimensions. For example, active markers 118 mayinclude infrared-emitting markers that are activated by an electricalsignal (e.g., infrared light emitting diodes (LEDs)), and passivemarkers 118 may include retro-reflective markers that reflect infraredlight (e.g., they reflect incoming IR radiation into the direction ofthe incoming light), for example, emitted by illuminators on the camera200 or other suitable device.

FIGS. 1 and 2 illustrate a potential configuration for the placement ofthe surgical robot system 100 in an operating room environment. Forexample, the robot 102 may be positioned near or next to patient 210.Although depicted near the head of the patient 210, it will beappreciated that the robot 102 can be positioned at any suitablelocation near the patient 210 depending on the area of the patient 210undergoing the operation. The camera 200 may be separated from the robotsystem 100 and positioned at the foot of patient 210. This locationallows the camera 200 to have a direct visual line of sight to thesurgical field 208. Again, it is contemplated that the camera 200 may belocated at any suitable position having line of sight to the surgicalfield 208. In the configuration shown, the surgeon 120 may be positionedacross from the robot 102, but is still able to manipulate the endeffector 112 and the display 110. A surgical assistant 126 may bepositioned across from the surgeon 120 again with access to both the endeffector 112 and the display 110. If desired, the locations of thesurgeon 120 and the assistant 126 may be reversed. The traditional areasfor the anesthesiologist 122 and the nurse or scrub tech 124 remainunimpeded by the locations of the robot 102 and camera 200.

With respect to the other components of the robot 102, the display 110can be attached to the surgical robot 102 and in other exemplaryembodiments, display 110 can be detached from surgical robot 102, eitherwithin a surgical room with the surgical robot 102, or in a remotelocation. End effector 112 may be coupled to the robot arm 104 andcontrolled by at least one motor. In exemplary embodiments, end effector112 can comprise a guide tube 114, which is able to receive and orient asurgical instrument 608 (described further herein) used to performsurgery on the patient 210. As used herein, the term “end effector” isused interchangeably with the terms “end-effectuator” and “effectuatorelement.” Although generally shown with a guide tube 114, it will beappreciated that the end effector 112 may be replaced with any suitableinstrumentation suitable for use in surgery. In some embodiments, endeffector 112 can comprise any known structure for effecting the movementof the surgical instrument 608 in a desired manner.

The surgical robot 102 is able to control the translation andorientation of the end effector 112. The robot 102 is able to move endeffector 112 along x-, y-, and z-axes, for example. The end effector 112can be configured for selective rotation about one or more of the x-,y-, and z-axis, and a Z Frame axis (such that one or more of the EulerAngles (e.g., roll, pitch, and/or yaw) associated with end effector 112can be selectively controlled). In some exemplary embodiments, selectivecontrol of the translation and orientation of end effector 112 canpermit performance of medical procedures with significantly improvedaccuracy compared to conventional robots that utilize, for example, asix degree of freedom robot arm comprising only rotational axes. Forexample, the surgical robot system 100 may be used to operate on patient210, and robot arm 104 can be positioned above the body of patient 210,with end effector 112 selectively angled relative to the z-axis towardthe body of patient 210.

In some exemplary embodiments, the position of the surgical instrument608 can be dynamically updated so that surgical robot 102 can be awareof the location of the surgical instrument 608 at all times during theprocedure. Consequently, in some exemplary embodiments, surgical robot102 can move the surgical instrument 608 to the desired position quicklywithout any further assistance from a physician (unless the physician sodesires). In some further embodiments, surgical robot 102 can beconfigured to correct the path of the surgical instrument 608 if thesurgical instrument 608 strays from the selected, preplanned trajectory.In some exemplary embodiments, surgical robot 102 can be configured topermit stoppage, modification, and/or manual control of the movement ofend effector 112 and/or the surgical instrument 608. Thus, in use, inexemplary embodiments, a physician or other user can operate the system100, and has the option to stop, modify, or manually control theautonomous movement of end effector 112 and/or the surgical instrument608. Further details of surgical robot system 100 including the controland movement of a surgical instrument 608 by surgical robot 102 can befound in co-pending U.S. patent application Ser. No. 13/924,505, whichis incorporated herein by reference in its entirety.

The robotic surgical system 100 can comprise one or more trackingmarkers 118 configured to track the movement of robot arm 104, endeffector 112, patient 210, and/or the surgical instrument 608 in threedimensions. In exemplary embodiments, a plurality of tracking markers118 can be mounted (or otherwise secured) thereon to an outer surface ofthe robot 102, such as, for example and without limitation, on base 106of robot 102, on robot arm 104, or on the end effector 112. In exemplaryembodiments, at least one tracking marker 118 of the plurality oftracking markers 118 can be mounted or otherwise secured to the endeffector 112. One or more tracking markers 118 can further be mounted(or otherwise secured) to the patient 210. In exemplary embodiments, theplurality of tracking markers 118 can be positioned on the patient 210spaced apart from the surgical field 208 to reduce the likelihood ofbeing obscured by the surgeon, surgical tools, or other parts of therobot 102. Further, one or more tracking markers 118 can be furthermounted (or otherwise secured) to the surgical tools 608 (e.g., a screwdriver, dilator, implant inserter, or the like). Thus, the trackingmarkers 118 enable each of the marked objects (e.g., the end effector112, the patient 210, and the surgical tools 608) to be tracked by therobot 102. In exemplary embodiments, system 100 can use trackinginformation collected from each of the marked objects to calculate theorientation and location, for example, of the end effector 112, thesurgical instrument 608 (e.g., positioned in the tube 114 of the endeffector 112), and the relative position of the patient 210.

In exemplary embodiments, one or more of markers 118 may be opticalmarkers. In some embodiments, the positioning of one or more trackingmarkers 118 on end effector 112 can maximize the accuracy of thepositional measurements by serving to check or verify the position ofend effector 112. Further details of surgical robot system 100 includingthe control, movement and tracking of surgical robot 102 and of asurgical instrument 608 can be found in co-pending U.S. patentapplication Ser. No. 13/924,505, which is incorporated herein byreference in its entirety.

Exemplary embodiments include one or more markers 118 coupled to thesurgical instrument 608. In exemplary embodiments, these markers 118,for example, coupled to the patient 210 and surgical instruments 608, aswell as markers 118 coupled to the end effector 112 of the robot 102 cancomprise conventional infrared light-emitting diodes (LEDs) or anOptotrak® diode capable of being tracked using a commercially availableinfrared optical tracking system such as Optotrak®. Optotrak® is aregistered trademark of Northern Digital Inc., Waterloo, Ontario,Canada. In other embodiments, markers 118 can comprise conventionalreflective spheres capable of being tracked using a commerciallyavailable optical tracking system such as Polaris Spectra. PolarisSpectra is also a registered trademark of Northern Digital, Inc. In anexemplary embodiment, the markers 118 coupled to the end effector 112are active markers which comprise infrared light-emitting diodes whichmay be turned on and off, and the markers 118 coupled to the patient 210and the surgical instruments 608 comprise passive reflective spheres.

In exemplary embodiments, light emitted from and/or reflected by markers118 can be detected by camera 200 and can be used to monitor thelocation and movement of the marked objects. In alternative embodiments,markers 118 can comprise a radio-frequency and/or electromagneticreflector or transceiver and the camera 200 can include or be replacedby a radio-frequency and/or electromagnetic transceiver.

Similar to surgical robot system 100, FIG. 3 illustrates a surgicalrobot system 300 and camera stand 302, in a docked configuration,consistent with an exemplary embodiment of the present disclosure.Surgical robot system 300 may comprise a robot 301 including a display304, upper arm 306, lower arm 308, end effector 310, vertical column312, casters 314, cabinet 316, tablet drawer 318, connector panel 320,control panel 322, and ring of information 324. Camera stand 302 maycomprise camera 326. These components are described in greater withrespect to FIG. 5. FIG. 3 illustrates the surgical robot system 300 in adocked configuration where the camera stand 302 is nested with the robot301, for example, when not in use. It will be appreciated by thoseskilled in the art that the camera 326 and robot 301 may be separatedfrom one another and positioned at any appropriate location during thesurgical procedure, for example, as shown in FIGS. 1 and 2. FIG. 4illustrates a base 400 consistent with an exemplary embodiment of thepresent disclosure. Base 400 may be a portion of surgical robot system300 and comprise cabinet 316. Cabinet 316 may house certain componentsof surgical robot system 300 including but not limited to a battery 402,a power distribution module 404, a platform interface board module 406,a computer 408, a handle 412, and a tablet drawer 414. The connectionsand relationship between these components is described in greater detailwith respect to FIG. 5.

FIG. 5 illustrates a block diagram of certain components of an exemplaryembodiment of surgical robot system 300. Surgical robot system 300 maycomprise platform subsystem 502, computer subsystem 504, motion controlsubsystem 506, and tracking subsystem 532. Platform subsystem 502 mayfurther comprise battery 402, power distribution module 404, platforminterface board module 406, and tablet charging station 534. Computersubsystem 504 may further comprise computer 408, display 304, andspeaker 536. Motion control subsystem 506 may further comprise drivercircuit 508, motors 510, 512, 514, 516, 518, stabilizers 520, 522, 524,526, end effector 310, and controller 538. Tracking subsystem 532 mayfurther comprise position sensor 540 and camera converter 542. System300 may also comprise a foot pedal 544 and tablet 546.

Input power is supplied to system 300 via a power source 548 which maybe provided to power distribution module 404. Power distribution module404 receives input power and is configured to generate different powersupply voltages that are provided to other modules, components, andsubsystems of system 300. Power distribution module 404 may beconfigured to provide different voltage supplies to platform interfacemodule 406, which may be provided to other components such as computer408, display 304, speaker 536, driver 508 to, for example, power motors512, 514, 516, 518 and end effector 310, motor 510, ring 324, cameraconverter 542, and other components for system 300 for example, fans forcooling the electrical components within cabinet 316.

Power distribution module 404 may also provide power to other componentssuch as tablet charging station 534 that may be located within tabletdrawer 318. Tablet charging station 534 may be in wireless or wiredcommunication with tablet 546 for charging table 546. Tablet 546 may beused by a surgeon consistent with the present disclosure and describedherein. Power distribution module 404 may also be connected to battery402, which serves as temporary power source in the event that powerdistribution module 404 does not receive power from input power 548. Atother times, power distribution module 404 may serve to charge battery402 if necessary.

Other components of platform subsystem 502 may also include connectorpanel 320, control panel 322, and ring 324. Connector panel 320 mayserve to connect different devices and components to system 300 and/orassociated components and modules. Connector panel 320 may contain oneor more ports that receive lines or connections from differentcomponents. For example, connector panel 320 may have a ground terminalport that may ground system 300 to other equipment, a port to connectfoot pedal 544 to system 300, a port to connect to tracking subsystem532, which may comprise position sensor 540, camera converter 542, andcameras 326 associated with camera stand 302. Connector panel 320 mayalso include other ports to allow USB, Ethernet, HDMI communications toother components, such as computer 408.

Control panel 322 may provide various buttons or indicators that controloperation of system 300 and/or provide information regarding system 300.For example, control panel 322 may include buttons to power on or offsystem 300, lift or lower vertical column 312, and lift or lowerstabilizers 520-526 that may be designed to engage casters 314 to locksystem 300 from physically moving. Other buttons may stop system 300 inthe event of an emergency, which may remove all motor power and applymechanical brakes to stop all motion from occurring. Control panel 322may also have indicators notifying the user of certain system conditionssuch as a line power indicator or status of charge for battery 402.

Ring 324 may be a visual indicator to notify the user of system 300 ofdifferent modes that system 300 is operating under and certain warningsto the user.

Computer subsystem 504 includes computer 408, display 304, and speaker536. Computer 504 includes an operating system and software to operatesystem 300. Computer 504 may receive and process information from othercomponents (for example, tracking subsystem 532, platform subsystem 502,and/or motion control subsystem 506) in order to display information tothe user. Further, computer subsystem 504 may also include speaker 536to provide audio to the user.

Tracking subsystem 532 may include position sensor 504 and converter542. Tracking subsystem 532 may correspond to camera stand 302 includingcamera 326 as described with respect to FIG. 3. Position sensor 504 maybe camera 326. Tracking subsystem may track the location of certainmarkers that are located on the different components of system 300and/or instruments used by a user during a surgical procedure. Thistracking may be conducted in a manner consistent with the presentdisclosure including the use of infrared technology that tracks thelocation of active or passive elements, such as LEDs or reflectivemarkers, respectively. The location, orientation, and position ofstructures having these types of markers may be provided to computer 408which may be shown to a user on display 304. For example, a surgicalinstrument 608 having these types of markers and tracked in this manner(which may be referred to as a navigational space) may be shown to auser in relation to a three dimensional image of a patient's anatomicalstructure. Motion control subsystem 506 may be configured to physicallymove vertical column 312, upper arm 306, lower arm 308, or rotate endeffector 310. The physical movement may be conducted through the use ofone or more motors 510-518. For example, motor 510 may be configured tovertically lift or lower vertical column 312. Motor 512 may beconfigured to laterally move upper arm 308 around a point of engagementwith vertical column 312 as shown in FIG. 3. Motor 514 may be configuredto laterally move lower arm 308 around a point of engagement with upperarm 308 as shown in FIG. 3. Motors 516 and 518 may be configured to moveend effector 310 in a manner such that one may control the roll and onemay control the tilt, thereby providing multiple angles that endeffector 310 may be moved. These movements may be achieved by controller538 which may control these movements through load cells disposed on endeffector 310 and activated by a user engaging these load cells to movesystem 300 in a desired manner.

Moreover, system 300 may provide for automatic movement of verticalcolumn 312, upper arm 306, and lower arm 308 through a user indicatingon display 304 (which may be a touchscreen input device) the location ofa surgical instrument or component on three dimensional image of thepatient's anatomy on display 304. The user may initiate this automaticmovement by stepping on foot pedal 544 or some other input means.

FIG. 6 illustrates a surgical robot system 600 consistent with anexemplary embodiment. Surgical robot system 600 may comprise endeffector 602, robot arm 604, guide tube 606, instrument 608, and robotbase 610. Instrument tool 608 may be attached to a tracking array 612including one or more tracking markers (such as markers 118) and have anassociated trajectory 614. Trajectory 614 may represent a path ofmovement that instrument tool 608 is configured to travel once it ispositioned through or secured in guide tube 606, for example, a path ofinsertion of instrument tool 608 into a patient. In an exemplaryoperation, robot base 610 may be configured to be in electroniccommunication with robot arm 604 and end effector 602 so that surgicalrobot system 600 may assist a user (for example, a surgeon) in operatingon the patient 210. Surgical robot system 600 may be consistent withpreviously described surgical robot system 100 and 300.

A tracking array 612 may be mounted on instrument 608 to monitor thelocation and orientation of instrument tool 608. The tracking array 612may be attached to an instrument 608 and may comprise tracking markers804. As best seen in FIG. 8, tracking markers 804 may be, for example,light emitting diodes and/or other types of reflective markers (e.g.,markers 118 as described elsewhere herein). The tracking devices may beone or more line of sight devices associated with the surgical robotsystem. As an example, the tracking devices may be one or more cameras200, 326 associated with the surgical robot system 100, 300 and may alsotrack tracking array 612 for a defined domain or relative orientationsof the instrument 608 in relation to the robot arm 604, the robot base610, end effector 602, and/or the patient 210. The tracking devices maybe consistent with those structures described in connection with camerastand 302 and tracking subsystem 532.

FIGS. 7A, 7B, and 7C illustrate a top view, front view, and side view,respectively, of end effector 602 consistent with an exemplaryembodiment. End effector 602 may comprise one or more tracking markers702. Tracking markers 702 may be light emitting diodes or other types ofactive and passive markers, such as tracking markers 118 that have beenpreviously described. In an exemplary embodiment, the tracking markers702 are active infrared-emitting markers that are activated by anelectrical signal (e.g., infrared light emitting diodes (LEDs)). Thus,tracking markers 702 may be activated such that the infrared markers 702are visible to the camera 200, 326 or may be deactivated such that theinfrared markers 702 are not visible to the camera 200, 326. Thus, whenthe markers 702 are active, the end effector 602 may be controlled bythe system 100, 300, 600, and when the markers 702 are deactivated, theend effector 602 may be locked in position and unable to be moved by thesystem 100, 300, 600.

Markers 702 may be disposed on or within end effector 602 in a mannersuch that the markers 702 are visible by one or more cameras 200, 326 orother tracking devices associated with the surgical robot system 100,300, 600. The camera 200, 326 or other tracking devices may track endeffector 602 as it moves to different positions and viewing angles byfollowing the movement of tracking markers 702. The location of markers702 and/or end effector 602 may be shown on a display 110, 304associated with the surgical robot system 100, 300, 600, for example,display 110 as shown in FIG. 2 and/or display 304 shown in FIG. 3. Thisdisplay 110, 304 may allow a user to ensure that end effector 602 is ina desirable position in relation to robot arm 604, robot base 610, thepatient 210, and/or the user.

For example, as shown in FIG. 7A, markers 702 may be placed around thesurface of end effector 602 so that a tracking device placed away fromthe surgical field 208 and facing toward the robot 102, 301 and thecamera 200, 326 is able to view at least 3 of the markers 702 through arange of common orientations of the end effector 602 relative to thetracking device 100, 300, 600. For example, distribution of markers 702in this way allows end effector 602 to be monitored by the trackingdevices when end effector 602 is translated and rotated in the surgicalfield 208.

In addition, in exemplary embodiments, end effector 602 may be equippedwith infrared (IR) receivers that can detect when an external camera200, 326 is getting ready to read markers 702. Upon this detection, endeffector 602 may then illuminate markers 702. The detection by the IRreceivers that the external camera 200, 326 is ready to read markers 702may signal the need to synchronize a duty cycle of markers 702, whichmay be light emitting diodes, to an external camera 200, 326. This mayalso allow for lower power consumption by the robotic system as a whole,whereby markers 702 would only be illuminated at the appropriate timeinstead of being illuminated continuously. Further, in exemplaryembodiments, markers 702 may be powered off to prevent interference withother navigation tools, such as different types of surgical instruments608.

FIG. 8 depicts one type of surgical instrument 608 including a trackingarray 612 and tracking markers 804. Tracking markers 804 may be of anytype described herein including but not limited to light emitting diodesor reflective spheres. Markers 804 are monitored by tracking devicesassociated with the surgical robot system 100, 300, 600 and may be oneor more of the line of sight cameras 200, 326. The cameras 200, 326 maytrack the location of instrument 608 based on the position andorientation of tracking array 612 and markers 804. A user, such as asurgeon 120, may orient instrument 608 in a manner so that trackingarray 612 and markers 804 are sufficiently recognized by the trackingdevice or camera 200, 326 to display instrument 608 and markers 804 on,for example, display 110 of the exemplary surgical robot system.

The manner in which a surgeon 120 may place instrument 608 into guidetube 606 of the end effector 602 and adjust the instrument 608 isevident in FIG. 8. The hollow tube or guide tube 114, 606 of the endeffector 112, 310, 602 is sized and configured to receive at least aportion of the surgical instrument 608. The guide tube 114, 606 isconfigured to be oriented by the robot arm 104 such that insertion andtrajectory for the surgical instrument 608 is able to reach a desiredanatomical target within or upon the body of the patient 210. Thesurgical instrument 608 may include at least a portion of a generallycylindrical instrument. Although a screw driver is exemplified as thesurgical tool 608, it will be appreciated that any suitable surgicaltool 608 may be positioned by the end effector 602. By way of example,the surgical instrument 608 may include one or more of a guide wire,cannula, a retractor, a drill, a reamer, a screw driver, an insertiontool, a removal tool, or the like. Although the hollow tube 114, 606 isgenerally shown as having a cylindrical configuration, it will beappreciated by those of skill in the art that the guide tube 114, 606may have any suitable shape, size and configuration desired toaccommodate the surgical instrument 608 and access the surgical site.

FIGS. 9A-9C illustrate end effector 602 and a portion of robot arm 604consistent with an exemplary embodiment. End effector 602 may furthercomprise body 1202 and clamp 1204. Clamp 1204 may comprise handle 1206,balls 1208, spring 1210, and lip 1212. Robot arm 604 may furthercomprise depressions 1214, mounting plate 1216, lip 1218, and magnets1220.

End effector 602 may mechanically interface and/or engage with thesurgical robot system and robot arm 604 through one or more couplings.For example, end effector 602 may engage with robot arm 604 through alocating coupling and/or a reinforcing coupling. Through thesecouplings, end effector 602 may fasten with robot arm 604 outside aflexible and sterile barrier. In an exemplary embodiment, the locatingcoupling may be a magnetically kinematic mount and the reinforcingcoupling may be a five bar over center clamping linkage.

With respect to the locating coupling, robot arm 604 may comprisemounting plate 1216, which may be non-magnetic material, one or moredepressions 1214, lip 1218, and magnets 1220. Magnet 1220 is mountedbelow each of depressions 1214. Portions of clamp 1204 may comprisemagnetic material and be attracted by one or more magnets 1220. Throughthe magnetic attraction of clamp 1204 and robot arm 604, balls 1208become seated into respective depressions 1214. For example, balls 1208as shown in FIG. 9B would be seated in depressions 1214 as shown in FIG.9A. This seating may be considered a magnetically-assisted kinematiccoupling. Magnets 1220 may be configured to be strong enough to supportthe entire weight of end effector 602 regardless of the orientation ofend effector 602. The locating coupling may be any style of kinematicmount that uniquely restrains six degrees of freedom.

With respect to the reinforcing coupling, portions of clamp 1204 may beconfigured to be a fixed ground link and as such clamp 1204 may serve asa five bar linkage. Closing clamp handle 1206 may fasten end effector602 to robot arm 604 as lip 1212 and lip 1218 engage clamp 1204 in amanner to secure end effector 602 and robot arm 604. When clamp handle1206 is closed, spring 1210 may be stretched or stressed while clamp1204 is in a locked position. The locked position may be a position thatprovides for linkage past center. Because of a closed position that ispast center, the linkage will not open absent a force applied to clamphandle 1206 to release clamp 1204. Thus, in a locked position endeffector 602 may be robustly secured to robot arm 604.

Spring 1210 may be a curved beam in tension. Spring 1210 may becomprised of a material that exhibits high stiffness and high yieldstrain such as virgin PEEK (poly-ether-ether-ketone). The linkagebetween end effector 602 and robot arm 604 may provide for a sterilebarrier between end effector 602 and robot arm 604 without impedingfastening of the two couplings.

The reinforcing coupling may be a linkage with multiple spring members.The reinforcing coupling may latch with a cam or friction basedmechanism. The reinforcing coupling may also be a sufficiently powerfulelectromagnet that will support fastening end-effector 102 to robot arm604. The reinforcing coupling may be a multi-piece collar completelyseparate from either end effector 602 and/or robot arm 604 that slipsover an interface between end effector 602 and robot arm 604 andtightens with a screw mechanism, an over center linkage, or a cammechanism.

Referring to FIGS. 10 and 11, prior to or during a surgical procedure,certain registration procedures may be conducted in order to trackobjects and a target anatomical structure of the patient 210 both in anavigation space and an image space. In order to conduct suchregistration, a registration system 1400 may be used as illustrated inFIG. 10.

In order to track the position of the patient 210, a patient trackingdevice 116 may include a patient fixation instrument 1402 to be securedto a rigid anatomical structure of the patient 210 and a dynamicreference base (DRB) 1404 may be securely attached to the patientfixation instrument 1402. For example, patient fixation instrument 1402may be inserted into opening 1406 of dynamic reference base 1404.Dynamic reference base 1404 may contain markers 1408 that are visible totracking devices, such as tracking subsystem 532. These markers 1408 maybe optical markers or reflective spheres, such as tracking markers 118,as previously discussed herein.

Patient fixation instrument 1402 is attached to a rigid anatomy of thepatient 210 and may remain attached throughout the surgical procedure.In an exemplary embodiment, patient fixation instrument 1402 is attachedto a rigid area of the patient 210, for example, a bone that is locatedaway from the targeted anatomical structure subject to the surgicalprocedure. In order to track the targeted anatomical structure, dynamicreference base 1404 is associated with the targeted anatomical structurethrough the use of a registration fixture that is temporarily placed onor near the targeted anatomical structure in order to register thedynamic reference base 1404 with the location of the targeted anatomicalstructure.

A registration fixture 1410 is attached to patient fixation instrument1402 through the use of a pivot arm 1412. Pivot arm 1412 is attached topatient fixation instrument 1402 by inserting patient fixationinstrument 1402 through an opening 1414 of registration fixture 1410.Pivot arm 1412 is attached to registration fixture 1410 by, for example,inserting a knob 1416 through an opening 1418 of pivot arm 1412.

Using pivot arm 1412, registration fixture 1410 may be placed over thetargeted anatomical structure and its location may be determined in animage space and navigation space using tracking markers 1420 and/orfiducials 1422 on registration fixture 1410. Registration fixture 1410may contain a collection of markers 1420 that are visible in anavigational space (for example, markers 1420 may be detectable bytracking subsystem 532). Tracking markers 1420 may be optical markersvisible in infrared light as previously described herein. Registrationfixture 1410 may also contain a collection of fiducials 1422, forexample, such as bearing balls, that are visible in an imaging space(for example, a three dimension CT image). As described in greaterdetail with respect to FIG. 11, using registration fixture 1410, thetargeted anatomical structure may be associated with dynamic referencebase 1404 thereby allowing depictions of objects in the navigationalspace to be overlaid on images of the anatomical structure. Dynamicreference base 1404, located at a position away from the targetedanatomical structure, may become a reference point thereby allowingremoval of registration fixture 1410 and/or pivot arm 1412 from thesurgical area.

FIG. 11 provides an exemplary method 1500 for registration consistentwith the present disclosure. Method 1500 begins at step 1502 wherein agraphical representation (or image(s)) of the targeted anatomicalstructure may be imported into system 100, 300 600, for example computer408. The graphical representation may be three dimensional CT or afluoroscope scan of the targeted anatomical structure of the patient 210which includes registration fixture 1410 and a detectable imagingpattern of fiducials 1420.

At step 1504, an imaging pattern of fiducials 1420 is detected andregistered in the imaging space and stored in computer 408. Optionally,at this time at step 1506, a graphical representation of theregistration fixture 1410 may be overlaid on the images of the targetedanatomical structure.

At step 1508, a navigational pattern of registration fixture 1410 isdetected and registered by recognizing markers 1420. Markers 1420 may beoptical markers that are recognized in the navigation space throughinfrared light by tracking subsystem 532 via position sensor 540. Thus,the location, orientation, and other information of the targetedanatomical structure is registered in the navigation space. Therefore,registration fixture 1410 may be recognized in both the image spacethrough the use of fiducials 1422 and the navigation space through theuse of markers 1420. At step 1510, the registration of registrationfixture 1410 in the image space is transferred to the navigation space.This transferal is done, for example, by using the relative position ofthe imaging pattern of fiducials 1422 compared to the position of thenavigation pattern of markers 1420.

At step 1512, registration of the navigation space of registrationfixture 1410 (having been registered with the image space) is furthertransferred to the navigation space of dynamic registration array 1404attached to patient fixture instrument 1402. Thus, registration fixture1410 may be removed and dynamic reference base 1404 may be used to trackthe targeted anatomical structure in both the navigation and image spacebecause the navigation space is associated with the image space.

At steps 1514 and 1516, the navigation space may be overlaid on theimage space and objects with markers visible in the navigation space(for example, surgical instruments 608 with optical markers 804). Theobjects may be tracked through graphical representations of the surgicalinstrument 608 on the images of the targeted anatomical structure.

FIGS. 12A-12B illustrate imaging devices 1304 that may be used inconjunction with robot systems 100, 300, 600 to acquire pre-operative,intra-operative, post-operative, and/or real-time image data of patient210. Any appropriate subject matter may be imaged for any appropriateprocedure using the imaging system 1304. The imaging system 1304 may beany imaging device such as imaging device 1306 and/or a C-arm 1308device. It may be desirable to take x-rays of patient 210 from a numberof different positions, without the need for frequent manualrepositioning of patient 210 which may be required in an x-ray system.As illustrated in FIG. 12A, the imaging system 1304 may be in the formof a C-arm 1308 that includes an elongated C-shaped member terminatingin opposing distal ends 1312 of the “C” shape. C-shaped member 1130 mayfurther comprise an x-ray source 1314 and an image receptor 1316. Thespace within C-arm 1308 of the arm may provide room for the physician toattend to the patient substantially free of interference from x-raysupport structure 1318. As illustrated in FIG. 12B, the imaging systemmay include imaging device 1306 having a gantry housing 1324 attached toa support structure imaging device support structure 1328, such as awheeled mobile cart 1330 with wheels 1332, which may enclose an imagecapturing portion, not illustrated. The image capturing portion mayinclude an x-ray source and/or emission portion and an x-ray receivingand/or image receiving portion, which may be disposed about one hundredand eighty degrees from each other and mounted on a rotor (notillustrated) relative to a track of the image capturing portion. Theimage capturing portion may be operable to rotate three hundred andsixty degrees during image acquisition. The image capturing portion mayrotate around a central point and/or axis, allowing image data ofpatient 210 to be acquired from multiple directions or in multipleplanes. Although certain imaging systems 1304 are exemplified herein, itwill be appreciated that any suitable imaging system may be selected byone of ordinary skill in the art.

FIGS. 13-17 illustrate exemplary images, systems, and/or methods formeasuring the depth of surgical instrumentation during an operation on apatient. Implementations of the measurement systems and methodsdescribed may be conducted by the robot systems as previously describedincluding robot systems 100, 300, and 600 and the components discussedthereto.

As an exemplary embodiment, a surgeon may position a long shaft such asa dilator tube within a secondary tracked tube, such as the robot's endeffector guide tube or a free tracked external guide tube, to a knowndepth. These components have also been discussed as noted above. Thedepth may be the exact depth needed such that the dilator tube contactsthe target bone of the patient. By referencing the secondary trackedtube, measuring the depth of the dilator tube may be conducted withouttracking the dilator tube itself.

Depth measurements may be based on the tracked guide tube—either therobot's end effector guide tube or other navigated guide tube—being in a“tube-centric” view. As an example, viewplanes of various CT scans of apatient's target bone may be chosen such that the 3D-tracked position ofthe guide tube (for example, positional tracking as earlier discussed)is aligned to be simultaneously within two non-parallel planes, or inother words coincident with the line formed by the intersection of twoplanes. For example, in a posterior surgery where the guide tube isaligned such that it is aimed down a pedicle of a vertebral body, twosubstantially orthogonal anatomical viewplanes may be selected such thatone viewplane is predominantly sagittal, with the guide tube alignedalong the vertical axis of the 2D viewplane, while the other viewplaneis predominantly axial, with the guide tube also aligned along that 2Dviewplane's vertical axis. FIG. 13 illustrates an exemplary 2D imageplane (slice) 1600 through a 3D computed tomography (CT) image volumeshowing vertebrae of a patient, including vertebral body 1602, a guidetube 1604, and vector 1606 from a sagittal viewpoint of the patient.FIG. 14 illustrates an exemplary 2D image plane (slice) 1700 through a3D CT image volume showing vertebral body 1602, guide 1604, and vector1606 from an axial view point of the patient.

Although FIGS. 13 and 14 show particular viewplanes, other pairs ofviewplanes could be selected such that the tracked guide tube's centralaxis is coincident with the line found from the intersection of the twoplanes. In addition, the 2D representation on each plane of the tubedoes not need to be vertical or even in the same direction in the twoplanes.

Vector 1606 may be depicted as extending from a representation of guidetube 1604 and overlaid on the images 1600 and 1700. On vector 1606,measurements may be shown incrementally with tick or hatch marks 1608.Marks 1608 may start from one end of guide tube 1604 (such as the top ofproximal end 1610 and represented as position zero), with measurementincreasing toward and beyond a distal end of the guide tube 1612. Guidetube 1604 may be coincident with the viewplanes because it is then knownthat any anatomical point along vector 1606 is reachable by a toolinserted through guide tube 1606. If guide tube 1604 was not coincidentwith the viewplanes, a vector may still be drawn but the vector may aprojection on the 2D view that may not intersect the anatomy visualizedon the viewplane.

Marks 1608 on vector 1606 may be toggled on or off as needed.Additionally, as a user independently zooms in or out on a viewplane,the frequency and labeling of marks 1608 may be automatically modifiedto minimize clutter while still providing useful information to the userregarding the depth. For example, as shown in images 1800, 1900, and2000 of FIGS. 15, 16, and 17, respectively, labels 1802 could beincluded at a rate of one label every 20 mm and marks 1606 at a rate ofone hatch mark every 10 mm for a particular level of zoom (See FIG. 15).As zoom is increased to 1.5 times the original zoom (compare FIG. 16 toFIG. 15), labels 1802 could automatically switch to a rate of one labelevery 10 mm and marks 1606 could automatically switch to a rate of onehatch mark every 5 mm. Then, as zoom is increased to 3.0 times theoriginal zoom (compare FIG. 17 to FIGS. 15 and 16), labels 1802 couldautomatically switch to a rate of one label every 5 mm and the marks1606 could automatically switch to a rate of one hatch mark every 2.5mm.

As an example, the decision for automatically switching rate andfrequency of marks 1606 and labels 1802 could be that between two pointsA and B, marks 1606 may be present from the first to the last visiblepoint on a line crossing the viewplane along the guide tube's centralvector. Within points A and B, an optimal selection would involveincrements representing well rounded values, such as tens, fives, ones,halves, and quarters. The frequency of labeling may be a rate of onelabel every C marks. For example, these rules would be able to dictatethe behavior shown in FIGS. 15-17 if A=10, B=15, C=2. With zooming, thesurgeon could read with good precision the distance from the top of theguide tube to the bone, for example 149 mm in FIGS. 15-17.

Using this measurement technique, the inserted instrument or dilator mayhave graduated markings and labels starting at zero at the distal end ofthe instrument and increasing toward the proximal end. FIG. 18 depictsan instrument 2100 with graduated markings 2102 showing this example.Markings 2102 may be present along the entire length of instrument 2100.In many cases, it may be unnecessary to include markings 2102 along thefirst length of instrument 2100 until the length of guide tube 1604 hasbeen exceeded since markings 2102 would not be visible at the proximalend of guide tube 1604 with instrument 2100 inserted into guide tube1604 and just beginning to protrude distally.

FIG. 19 illustrates instrument 2100, with markings 2102, inserted intoguide tube 1604. The surgeon would insert instrument 2100 with markingsinto the tracked guide tube 1604 and would read the position of theinserted instrument 2100 from its graduations or markings 2102. Thisreading may indicate whether instrument 2100 reached the desired depth.For example, when inserting a dilator, if the length observed onmarkings 2102 agrees with a length measured from the measurementrepresenting the distance from the proximal end of guide tube 1604 tothe target bone of the patient, the surgeon would know that instrument2100 was touching the target bone. If the length read from instrument2100 was 3 mm less than the length from the measurement between theguide tube to the target bone, the surgeon would know that they mustinsert instrument 2100 a distance of 3 more millimeters before bonewould be touched.

As described above, a distance from the top tip of instrument 2100 tothe proximal end (top) of the tracked guide tube 1604 is being read frominstrument 2100 by the use of markings 2102. Under the same principlesof the present disclosure, measurement techniques may be configured suchthat the graphical images of the patient anatomy show the distance fromthe distal end (bottom) of tracked guide tube 1604, or the distance froma window through the guide tube 1604 to the tip of the instrument 2100.The insertion depth would then be read from these other locations, i.e.,from the bottom of the guide tube or observed through a window in theguide tube, to draw the same information about the depth of insertion ofthe instrument.

FIG. 20 illustrates a method 2200 for determining the distance or depthin order to contact a target bone of patient consistent with theprinciples of the present disclosure. At step 2202 a computer subsystem,such as those previously described, receives a scan, for example a CTscan, that may represent the target bone of a patient from differentviewplanes or viewpoints. The computer subsystem may receive a scan of afirst viewplane and a second viewplane that form an intersection ofviews of the target bone in an image space. At step 2204, the computersubsystem may receive information indicative of a position of a guidetube of the surgical robot system in navigational space. At step 2206the computer of the computer subsystem may determine a distance betweena distal portion of the guide tube to the target bone of the patient.The distance may be determined such that a central axis of the guidetube is coincident to the line of intersection formed between the firstviewplane and the second viewplane. At step 2608 the computer subsystemmay display a vector indicative of the distance to contact the targetbone of the patient on at least one of the first viewplane scan and thesecond viewplane scan. The vector may include any or all of theattributes a previously describe and those skilled in the art wouldrecognize that the visual depiction of the vector may be represented inother way to indicate distance measurements that would fall within thescope of the present disclosure.

While the invention has been disclosed in connection with the preferredembodiments shown and described in detail, various modifications andimprovements thereon will become readily apparent to those skilled inthe art. Accordingly, the spirit and scope of the present invention isnot to be limited by the foregoing examples, but is to be understood inthe broadest sense allowable by law.

What is claimed is:
 1. A surgical robot system configured to determine adistance for a surgical instrument to contact a target bone of a patientduring a surgical operation, said system comprising: a guide tubecomprising a tracking marker and wherein the guide tube is configured toreceive the surgical instrument; a tracking subsystem having a positionsensor that recognizes the tracking marker in a navigational space; aplatform interface module configured to receive a signal from thetracking subsystem indicative of a position of the guide tube based onthe tracking marker; a computer subsystem, including a computer and adisplay, configured to receive a first viewplane scan of the target boneand a second viewplane scan of the target bone, wherein the firstviewplane and the second viewplane form an intersection of views of thetarget bone, wherein the computer subsystem is configured to receive theposition of the guide tube from the platform interface module, andwherein the computer subsystem, via the display, is configured to depicta vector indicative of the distance to contact the target bone of thepatient, relative to a distal portion of the guide tube, on at least oneof the first viewplane scan and the second viewplane scan, and whereinthe vector represents a central axis of the guide tube being coincidentto the intersection.
 2. The system of claim 1, wherein the vectorcomprises markings indicating the distance between the distal portion ofthe guide tube to the target bone.
 3. The system of claim 2, wherein themarkings may be depicted in rounded increments.
 4. The system of claim2, wherein the depiction of the vector may be zoomed in or out.
 5. Thesystem of claim 2, wherein increments of the markings automaticallychanges based upon a level of zoom.
 6. The system of claim 1, furthercomprising the surgical instrument received in the guide tube.
 7. Thesystem of claim 6, wherein the surgical instrument contains graduatedmarkings indicating the actual depth of the surgical instrument past thedistal portion of the guide tube.
 8. The system of claim 1, wherein thefirst viewplane is a sagittal view plane with respect to the target boneand the second viewplane is an axial viewplane with respect to thetarget bone.
 9. The system of claim 1, further comprising anend-effector wherein the guide tube is part of the end effector.
 10. Thesystem of claim 1, further comprising an end-effector and wherein theguide tube is tracked separately from the end effector.
 11. A method fordetermining the distance for a surgical instrument to contact a targetbone of a patient during a surgical operating using a robotic surgicalsystem, said method comprising: receiving, by a computer subsystemhaving a computer and a display, a first viewplane scan of the targetbone and a second viewplane scan of the target bone, wherein the firstviewplane and the second viewplane form an intersection of views of thetarget bone in an image space; receiving, by the computer subsystem, aposition of a guide tube in navigational space; determining, by thecomputer, a distance between a distal portion of the guide tube to thetarget bone of the patient, wherein the distance is determined such thata central axis of the guide tube is coincident to the intersection; anddepicting, via the display, a vector indicative of the distance tocontact the target bone of the patient on at least one of the firstviewplane scan and the second viewplane scan.
 12. The method of claim11, wherein the vector comprises markings indicating the distancebetween the distal portion of the guide tube to the target bone.
 13. Themethod of claim 12, wherein the markings may be depicted in roundedincrements.
 14. The system of claim 12, wherein the depiction of thevector may be zoomed in or out.
 15. The method of claim 12, whereinincrements of the markings automatically changes based upon a level ofzoom.
 16. The method of claim 11, further comprising the surgicalinstrument received in the guide tube.
 17. The method of claim 16,wherein the surgical instrument contains graduated markings indicatingthe actual depth of the surgical instrument past the distal portion ofthe guide tube.
 18. The method of claim 11, wherein the first viewplaneis a sagittal view plane with respect to the target bone and the secondviewplane is an axial viewplane with respect to the target bone.
 19. Themethod of claim 11, further comprising an end-effector wherein the guidetube is part of the end effector.
 20. The method of claim 11, furthercomprising an end-effector and wherein the guide tube is trackedseparately from the end effector.